Background Ankylosing Spondylitis (AS) is a chronic inflammatory disease that mainly affects the spine, sacroiliac joints and entheses. The mSASSS index (modified Stoke Ankylosing Spondylitis Spinal Score) is typically used to assess damage of the spine at radiological level. AS produces in the vertebra erosions, sclerosis, squaring (mSASSS-1) and subsequently syndesmophytes (mSASSS-2) and in the worst cases bone bridges (mSASSS-3). Many studies have analyzed the complete index versus evolution time, gender, presence of HLAB27, etc. Analyzing individually each vertebra in patients it could be know if vertebrae deterioration progresses equally in all vertebra when more structural damage occurs.
Objectives To analyze vertebral distribution of structural damage in the spine of patients with ankylosing spondylitis according to the mSASSS index criteria.
Methods 103 AS patients (69 men and 34 women, mean age 41.9±11.1 years, 14.4±0.4 evolution years, 90% HLAB27 positive) participated in the study. Analyzing radiographic images of the lumbar and cervical spine, individual scores of structural damage were obtained at each vertebra, obtaining the mSASSS index. In addition the metrological index UCOASMI  and the activity index ASDAS was measured.
Results For each vertebra analyzed, the percentage of individuals with the vertebra affected (mSASSS≥1) and percentage with severe structural damage (mSASSS ≥2) are shown in graph. Severity ratio calculated as the ratio between these two parameters is represented in the secondary vertical scale. Average evolution time in years, structural damage (mSASSS), mobility (UCOASMI) and activity (ASDAS) categorized by gender and structural damage were also calculated (data not shown).
Conclusions This study has allowed to analyze the areas that are more often damaged in AS patients as it increases the degree of structural damage. The most affected are those belonging to the middle of the cervical and lumbar region (C5 and L4). The mSASSS index was higher in men than in women, a fact already known. The mobility according UCOASMI was decreasing as structural damage increases. The ASDAS index was similar in all groups (although statistical differences between men and women were found). Following a logical structure (sclerosis, quadrature, syndesmophyte and bone bridge) the vertebrae most commonly affected should have a greater presence of spinal fusion, however, according to the ratio of severity, are not the central but the extreme vertebrae which have a higher severity ratio. Especially in those vertebrae that have less mobility, bone bridges appear earlier. This can highlight the idea of the need of increased physical activity and exercise adequate flexibility in these patients to delay ankylosis.
Garrido-Castro JL, Escudero A, Medina-Carnicer R, Galisteo AM, Gonzalez-Navas C, Carmona L, Collantes-Estevez E. Validation of a new objective index to measure spinal mobility: the University of Cordoba Ankylosing Spondylitis Metrology Index (UCOASMI).Rheumatol Int. 2014 Mar;34(3):401-6. doi: 10.1007/s00296-013-2917-7. Epub 2013 Dec 20.
Disclosure of Interest None declared